Ferroelectric Polymers with Ultrahigh Energy Density, Low Loss, and Broad Operation Temperature for Navy Pulse Power Capacitors

Abstract

Abstract : The objective of this ONR program is to develop fundamental understanding on the material requirement of dielectric polymers in order to achieve high energy density with low loss and high dielectric strength. On the material front, the objective is to design and develop dielectric polymers of high energy density and low losses for pulse power applications. In the past three years, we have developed and investigated dielectric polymers with strongly coupled dipoles (modified PVDF based polymers) and their blends to achieve these objectives. Built upon the success of the polar-fluoropolymers, we have investigated a series of high temperature dielectrics with molecular units of high dipole moment and developed new class of polymer dielectrics based on aromatic polythiourea (ArPTU), which is capable of maintaining its low dielectric loss (high electric charge-discharge energy efficiency 90%) up to an ultra high operation fields ( 1 GV/m) with a very high electric energy density ( 24 J/cm3). To develop understanding of the molecular and nano-structure mechanisms, a systematic dielectric studies, including the thermal stimulated discharge current (TSDC) measurement, have been carried out. It was shown that it is the deep traps with high activation energy and large trap density in the PTU thin films that are responsible for the observed low conduction loss and high dielectric strength. Trap-limited high field conduction was studied by the electron hopping theory in the amorphous material.